How do I find the square footage of my house for free?

The county assessor website is the quickest free source -- search for your county assessor online and look up the property address. Zillow and Redfin also show square footage, but they pull from the same county records and reflect the same accuracy limitations. For the most accurate figure without field measurement, upload a to-scale floor plan to PlanSnapper to calculate GLA directly.

Is the square footage on Zillow accurate?

Often no. Zillow pulls square footage from county records and MLS listings, which are not always based on verified field measurements. Errors of 100-500 sq ft are common, particularly for homes with additions, finished basements, or assessor records that have not been updated since construction.

How do appraisers find a home's square footage?

Appraisers measure the home themselves from the exterior using the ANSI Z765 standard. They walk the perimeter with a laser measurer or tape, calculate the footprint of each above-grade floor, and total only the finished, heated, above-grade areas to arrive at GLA. This is why an appraiser's reported square footage often differs from assessor records or MLS listings.

Can I dispute the square footage my county has on record?

Yes. If your county assessor has the wrong square footage, you can file a correction request with supporting documentation such as an appraisal, building permit, or a verified measurement. Many counties accept corrections when accompanied by a licensed appraiser's report or survey. The process varies by jurisdiction but is worth pursuing if the error affects your property taxes.

What is the most accurate way to find my home's GLA without hiring an appraiser?

Uploading a to-scale floor plan to a GLA calculator like PlanSnapper is the most accurate method short of a full appraisal. County records and online listings are convenient but often reflect outdated or unverified figures. A to-scale floor plan measured by a professional or generated by a 3D scan tool will give you the closest estimate to what a licensed appraiser would report.

Why does square footage differ between Zillow, county records, and my appraisal?

Each source uses different data and may apply different measurement standards. County records come from permit history and assessor estimates. Zillow and Redfin pull from those same records. Appraisers measure from the exterior under ANSI Z765. Discrepancies of 3-8% are common and do not automatically indicate an error on any single source.

Does Redfin or Zillow show GLA or total square footage?

These platforms display whatever figure was entered in the MLS or sourced from county records. That figure may be GLA, total finished area, or an unspecified mixed number depending on who entered the data. For appraisal purposes, the only reliable square footage is a field-verified ANSI Z765 measurement.

Are Zillow and Redfin square footage numbers accurate?

Often not. Zillow and Redfin pull square footage from public records — tax assessor data, MLS listings, or both — which may be based on outdated measurements, self-reported owner estimates, or assessor methodology that differs from ANSI standards. Studies show MLS square footage errors of 5-10% are common. For an accurate figure, you need an appraiser measurement or a floor plan tracing from architectural drawings.

What is the most reliable free way to find a home's square footage?

The county assessor's website is the most accessible free source, but not necessarily the most accurate. For better accuracy, request the appraisal report if you are the homeowner (lenders are required to give you a copy). If you have a floor plan, upload it to PlanSnapper to calculate GLA yourself using ANSI methodology — this is free for the first five measurements.

Home / Learn / How to Find the Square Footage of Your House Online

Appraisal Practice · 5 min read

Part of: How to Measure Square Footage: The Complete Guide

How to Find the Square Footage of Your House Online

Public records, MLS data, and real estate portals each report square footage from different sources -- and they regularly disagree. Before going on-site, cross-referencing these sources helps establish what the assessor has on file, flag discrepancies, and anticipate where the prior square footage may be wrong. Here is how to read each source and what to do when they conflict.

Method 1 -- County Assessor Records (Most Reliable Free Source)

The county assessor's property database is the primary public record for square footage. Search "[county name] assessor property search" or "[county name] parcel search" to find the relevant portal for the subject property's jurisdiction.

The assessor record typically shows the recorded square footage, building area, year built, and in some cases a breakdown by level. This figure is useful as a baseline -- it represents what the jurisdiction has on file and what property tax assessments are based on.

Key limitation: assessor data is often based on permits or exterior estimates taken at time of construction or last major update. It may not reflect additions, conversions, or corrections made since. Assessors may also use interior measurement or their own GBA methodology rather than the exterior-based ANSI Z765 standard appraisers use -- which produces systematically different results. The assessor figure is a starting point for research, not a substitute for field measurement from the exterior.

Method 2 -- MLS, Zillow, and Redfin

MLS-sourced square footage on Zillow, Redfin, and Realtor.com traces back to one of two places: the county assessor record, or what the listing agent entered when the property was last listed. In most cases it is the assessor record, copied without verification.

When reviewing these figures pre-inspection, the more useful data point is whether the portal's figure matches the assessor record. A material discrepancy -- say, Redfin showing 2,400 sq ft against an assessor record of 1,900 sq ft -- is often a signal that the listing agent included finished basement area or an addition that the assessor hasn't yet recorded. Both scenarios warrant closer review on-site.

Method 3 -- Prior Appraisal Report

A prior appraisal report -- if available in the workfile, seller disclosures, or through the lender -- contains the most reliable square footage figure available without new field measurement. The GLA from a prior ANSI Z765-compliant appraisal is directly comparable to what a current appraisal will produce, assuming no changes to the structure since that date.

The sketch addendum is the key document: it shows exterior dimensions, floor-by-floor area calculations, and any deductions for stairwell voids or non-GLA areas. Comparing the prior sketch against the current assessor record quickly surfaces additions, discrepancies, or errors that need to be resolved during the inspection.

Method 4 -- Upload a Floor Plan to PlanSnapper (Most Accurate)

When a floor plan is available -- from a prior appraisal sketch, builder plans, county records, or a listing service like CubiCasa or Matterport -- PlanSnapper calculates GLA directly from it using the same exterior-perimeter methodology appraisers use. Upload the plan, trace the perimeter, set a scale reference from one known dimension, and get a calculated area in about 2 minutes. If you don't have a floor plan yet, see how to get a floor plan of an existing home.

This is useful for pre-inspection due diligence: you can verify whether the listed square footage is plausible before going on-site, and identify any floors or areas that need closer attention during field measurement.

Try Free -- Upload a Floor Plan

Why the Numbers Often Don't Match

Assessor records, MLS listings, and appraisal reports can all differ -- sometimes by hundreds of square feet -- without any of them being incorrect by their own methodology. The discrepancy is usually definitional.

ANSI Z765 defines GLA as above-grade, finished, heated area measured from the exterior. Assessors may use interior measurement, different inclusion rules, or building permit data. MLS figures entered by agents may include below-grade finished area, garages, or unheated spaces. A finished basement showing up in one source and not another accounts for the majority of large discrepancies.

Basements are excluded from GLA under ANSI Z765 regardless of finish level -- they are reported separately as below-grade finished area. Garages are always excluded. These two categories are the most common source of the gap between what public records show and what an appraiser will report. See: Are basements included in square footage?

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